The present invention relates to a new and improved method of producinhg a dyed and stabilized non-twisted fibre sliver, and to a new and improved dyed and stabilized fibre sliver the fibres of which are mutually bonded produced according to such method.
From the specification of the German Pat. application No. 1,510,377 laid open to public inspection it is already known to produce in the spinning mill dyed and stabilized non-twisted fibre slivers, the individual fibres of which are dyed and mutually bonded. According to this method a through-passing non-twisted fibre arrangement is impregnated with a liquid containing a binding agent and a dye. Subsequently, excessive liquid is squeezed off under application of pressure and the fibres are compressed or condensed at all sides into a compact sliver. After the binding agent is bonded under application of heat, i.e. under increased or elevated temperatue, and after drying the compact sliver, there is obtained the dyed and stabilized fibre sliver in which the fibres are mutually bonded by the binding agent. Even if the application of the binding agent and of the dye is effected in one and the same processing step, compatibility of the simultaneously applied binding agent and dye is required in a manner such that e.g. the bonding of the fibres is not influenced by the dye. This can be disadvantageous in certain cases.
A further disadvantage of this method is seen in that certain dyes and binding agents cannot be distributed, e.g. solved, sufficiently in one and the same liquid, and thus cannot be applied according to the proposed prior art method. This disadvantage makes itself felt e.g. if synthetic fibre materials are processed. Due to e.g. different affinities of a dye to various binding agents, in many cases application of a greater dye quantity is required than needed for dyeing the fibres in the sliver to a desired colour. Thus the simultaneous dyeing and bonding process not only becomes complicated but also economically unfavourable. It also has been found that the stabilized sliver produced by application of a binding agent can cause in the subsequent processes, e.g. in a subsequent drafting process and in a possible subsequent twist-imparting process to produce a yarn, or in directly weaving it, increased dust accumulation in the drafting a system or on the ring spinning frame, respectively, or on the loom, which is generated as the dryed binding agent is shed off while the bonds are broken during the drafting process or by friction respectively. Frequent cleaning of these devices thus is required if disturbances are to be avoided, which reduces the economic feasibility of the use of stabilized fibre slivers. Reduction of the binding agent quantity does not result in reduced dust or fly shedding, but reduces the stability or the strength respectively, of the fibre sliver in such manner that it no longer has the characteristics desired for further processing. Another disadvantage is seen in that in many cases an end product made from the stabilized fibre sliver must be washed for eliminating the binding agent which can influence in an undesirable manner the characteristics or properties of the end product, e.g. its hand.
From the publication or literature, as cited in "Chemiefasern/Textilindustrie," No. 8, 1973, pages 752 through 754, the production of non-woven end products is known, in which a latent solvent of a fibre material, i.e. a solvent not acting upon the fibre material at room temperature is sprayed or dripped either before carding onto the fibre material in a hopper feeder or a web thereof or after carding onto a fibre web. Subsequently the fibre assembly treated with the latent solvent is heated to a temperature at which the fibres are activated by the solvent, in which process the fibres are partially solved by the solvent and are mutually welded at their contact points and the latent solvent is evaporated. Also this so-called "solvent bonding" process permits bonding of fibres protruding from the fibre assembly in woven, knitted, tufted or non-woven products, i.e. also in end products also, in such a manner that the quantity of protruding fibres is reduced. For activating the latent solvent, hot air is guided through the web in such a manner that the web is supported by the air. The textile end products produced according to the solvent bonding process are of a structure which, owing to the solvent bonding, consists only of the bonded fibre material.
Spraying or dipping the latent solvent, however, does not permit sufficient wetting of a fibre assembly as considered over its whole thickness, and thus subsequently no uniform bonding action over the thickness of the fibre assembly can be effected. The fibre mass present in a hopper feeder, known to be large and to be randomly arranged, or the web or fabric of large dimensions thus can be wetted only on their surface or in a zone near the surface. In particular, in a woven fabric made from twisted yarns, no uniform wetting can be effected across the yarn as this process in hampered or precluded by the fibres closely arranged side by side due to the twist. For this reason also, using a dye solved in the latent solvent, it is not possible to achieve any satisfactory and uniform dyeing of such fibre assemblies as the fibre assembly also cannot be sufficiently wetted with the dye. In the known method, activating temperatures ranging from 60.degree. to 200.degree. C. are proposed, the coloration or dyeing, however, is not fast or durable. If a quantity of solvent, and thus also of dye, is applied, sufficient for obtaining sufficient wetting across the whole thickness, uniform wetting still cannot be achieved as, for the reasons mentioned above, the zones near the surface are wetted more intensively than the inside zones of the fibre assembly. Also, guiding hot air through the fibre assembly can be effected only with a fibre assembly in which the fibres or fibre aggregations are randomly oriented, such as e.g. in a web, or which has sufficient cohesion owing to twist or due to its woven construction. The known method thus is suitable merely for solvent bonding of more or less large fibre aggregations or twisted or woven yarns, which are bonded mutually, and is not applicable for a durable coloration completely throughout the fabric nor for mutually bonding the individual fibres of such fibre assemblies nor for a non-twisted fibre arrangement.
According to the British Pat. Specification No. 1,098,106 or the German Pat. application No. 1,958,472 laid open to public inspection, it is also known to dye yarns wound into a package, e.g. made from polyacrylonitrile fibres, in an aqueous solution of a basic or cationic dyestuff containing a chemical compound, e.g. tetramethylenesulfone, which in an aqueous solution partially solves or swells the fibres and thus makes possible a dyeing process at temperatures of 80.degree. C. at the highest. Before the yarns, in the method according to German Pat. application No. 1,958,472, wound into the package and treated with the dyestuff solution, are brought to a temperature of up to 100.degree. C. subsequently, the partially solving chemical compound is washed out first and at the temperature mentioned no longer can act on the fibre material.